Relatively sophisticated optical systems have been developed to produce separate red, green and blue colors which are converged to provide a light beam having any desired color. These known optical systems generally employ a combination of dichroic mirrors or filters combined with a plurality of white light sources to project separate red, green and blue light beams along a desired projection axis. These beams pass through a lens system to provide a mixed output beam of a desired color. Such colored light systems are illustrated by German Utility Model G86 265 26.1 to A. C. R. Braendli & Voegeliag as well as by U.S. Pat. Nos. 2,909,097 to Alden et al, 3,318,185 to Kott and 3,818,216 to Larraburu. In all of these patents, dichroic mirrors or filters are utilized to separate the light spectrum into red, blue and green colors. By varying the intensity of individual light sources, the intensity of individual colors is controlled, and when the colors are recombined and passed along a projection axis, the output color obtained can be varied.
In order to provide an almost infinite variety of lighting effects from lighting systems of the type described, recent systems have been developed which incorporate a central processor to control the individual intensity of each of a plurality of individual light sources. Such a system is illustrated by U.S. Pat. No. 4,622,881 to Rand which illustrates a visual display unit including at least three light sources for providing different colors. A central processor for the unit includes a central stored table where the average power levels for each of the lamps necessary to produce a desired color are stored. The table is accessed with a color number and intensity value, and these can be preprogrammed so that a complete subroutine can be accomplished under the control of the central processor. Also, audio processing circuitry is provided to produce outputs corresponding to amplitude, frequency distribution, envelope and tempo.
Similarly, U.S. Pat. No. 4,635,052 to Aoike et al discloses an image display device using a plurality of light units which provide a black and white rather than a colored light display. However, the intensity of the individual light units for this apparatus is controlled by an intensity control system involving comparators which receive a ramp signal from a sawtooth generator and an image signal from a central control device. The comparator output operates a switch which controls the high frequency voltage supplied to each individual light unit.
The processor controlled color lighting systems which have been previously developed operate effectively to provide a varying color display in response to either input music or a preprogrammed sequence. In both cases, variation in the intensity of individual light sources for red, blue and green light results in the variation in a single color transmitted along a projection axis. However, the aesthetic display provided by such units can be considerably improved by enhancing the light control provided. For example, the provision of digital light control of light sources facilitates the simultaneous use and control of a many individual sources of red, green and blue light with each source being accessed and accurately programmed by an individual control channel. Additionally, if the intensity control circuit for each light source is incorporated in a light fixture remote from the central processor control system, each light source can be rapidly and effectively programmed to respond to a specific control channel, and when desired, the light source can be preprogrammed to a different control channel.
Finally, a programmed display from a variable color lighting system employing a plurality of separately controlled light sources can be considerably enhanced, if, as a light source is programmed from one color intensity to another, it fades into the subsequent color intensity and all light sources reach their programmed intensity at the same time. If this can be accomplished, colors will fade and blend throughout the visible spectrum without the chopping or glitching that is normally associated with most mechanical and electrically controlled color changers.